Boss GE-7 For Boost or Tone Shaping

Using an equalizer to boost the guitar’s input signal makes a lot of sense. It provides a clean gain and a lot of headroom. Aside from boosting the signal, it can, of course, be used to carve out specific frequencies. Unlike most overdrive pedals, an equalizer has the ability to be very precise with multiple frequency bands and can create special effects.

The downside to this specific pedal is noise. It uses cheap tantalum capacitors in the signal path. This creates a hissing sound when the sliders are moved away from the zero mark. The MXR 10 Band EQ is reputedly better, but I don’t own it and can’t comment about it further.

Getting Active

Unlike the controls on an amplifier, a graphic EQ uses microchips to simulate an inductor and couples it with a resistor to amplify the boost or cut, giving it a much stronger affect. This is referred to as an active circuit, because it is actively engaged in changing the frequency by way of amplification.

Passive circuits, like the controls on most amplifiers, or a guitar’s tone control, work to cut the level of a set frequency, but do not amplify. They create a filter by passively being in the way.

Rubber Bands

I try to imagine the boosts and cuts made on a graphic EQ as if there were rubber bands connected to the sliders. While boosting at one of the octaves will certainly affect that band the most, there is a pull on the surrounding octaves, making them also rise or fall by varying amounts. The amount of pull on the neighboring bands depends on how heavy the boost or cut is. This width of the band is called “Q”. We’ll come back to this idea when talking about a cocked wah setting.

Boosting

A sweet boost setting for my Dual Rectifier.

Here’s an example of how I use the pedal as a boost. Notice that I barely use any boosts of the frequencies and instead use the level control to push the whole shape. In my experience, EQ works better when used to cut frequencies and the level control is better for increasing the overall size.

One other thing to note: as the level is increased, imagine the zero line moving in the opposite direction. In this case, the imaginary zero line would be down near where the 6.4k slider is set and the whole effect is a mid-peaked, wide band boost.

Boosting Alternative

Alternative boosting style; sounds filtered; can be noisy.

An alternate way to boost is to keep the level at zero and boost the frequencies which you want to enhance.

I have found this way to be a little odd. Boosting the individual frequencies with an inductive-resistive circuit is different from an overall increase in level. It produces a filtered sound. This is cool for some things, but I don’t find it useful for a primary tone. Also, the more a frequency is boosted, the more likely it is that noise will be introduced to the signal.

The Crying Chicken

Cocked Wah example. For a wah, the Q is a bit wide.

Here’s an example of a setting to imitate a cocked wah. A wah basically takes a small frequency band and filters out everything around it. A wah pedal can move this peak around, but a cocked wah is the same as if the wah was turned on and left sitting in a sweet spot.

It might appear that 400 Hz is the center frequency, but this is not so. Earlier I wrote that I imagine rubber bands being attached to the sliders to picture their interaction with each other. In this case, the 200 Hz band is higher than the 800 Hz slider. This causes the center frequency to shift a little lower, as the frequencies cut by 800 Hz slider are pulling the on frequencies boosted by the 400 Hz slider. If the 200 Hz and 800 Hz sliders were matched, 400 Hz would be the center of the peak.

Cocked Wah with smaller Q. Sounds more vocal.

The Q of a filter is the ratio of the width of the frequency, measured where it decreases by -3dB on each side of the peak, expressed in octaves (bandwidth). Q width is frequency dependent. Since this is an analog pedal, it isn’t going to be exactly determined and doesn’t have to be worked out (lucky for us). The important thing is to understand that the bandwidth needs to be limited to create a wah-like, vocal sound.

The overall objective, then, would be to try and find a comfortable, cool sounding, bandwidth. In the second cocked wah example, the 200 and 800 sliders could be adjusted up and down together to find where a person likes it most. Any band which is farther than 1 slider from the center frequency should be pulled down as far as possible and only increased by small amounts from -15 dB, if needed.

The 400 slider doesn’t have to determine the center; boost any slider and move its two neighbors until satisfied. Then, just adjust the Level control to correct issues with volume or to boost this filter.

There are a lot of things which can be done with an EQ pedal. Have fun and find your own, new, signature sounds.